Three employees were injured in a fire Tuesday morning at an electrical substation in the Loop.

The fire was caused by an arc blast relayed to a transformer shortly before 11:30 a.m. at a ComEd substation in the first block of East Lake, according to Chicago Fire Department spokesman Larry Merritt. The substation supplies power to the CTA and other parts of the grid.

Three workers were injured and taken to hospitals, Merritt said. Two of them were in critical condition while the third had been stabilized.

The fire has since been struck out and secured, fire officials said.

A ComEd spokesman said the incident did not involve ComEd equipment and the workers who were injured were not ComEd employees. About 500 outages were caused by the fire, but power was restored by about noon.

Further details were not immediately available.

Three workers were hurt in a fire Tuesday morning at an electrical substation in the Loop. | Fire Media Affairs